In an injection molding machine comprising a stationary and a movable mold plate, the force retaining the mold closed during the injection operation must be very substantial in order to resist the high pressures which occur during injection molding. The mold surfaces, therefore, can be subjected to great damages upon closing of the mold if, at the time of the preceding injection, a molded object should have been stuck between the mold halves. The resulting problems can be particularly serious in automatic operation because then the mold halves are not inspected between injections. Others have attempted to correct this problem in different forms of apparatus such as is shown in U.S. Pat. Nos. 2,801,442 and 3,564,657. In U.S. Pat. No. 2,801,442, the sensing of an object within the mold is achieved when pressure is being applied at a high level and, consequently, there can be damage to the molds before reversal of pressure if effected. Additionally, U.S. Pat. No. 3,564,657 is not directed to the same type of molding operation as the present invention, i.e., a two-part mold wherein high pressure is applied in order to withstand injection pressures. Rather, U.S. Pat. No. 3,564,657 is directed to a three-part mold without provision for low pressure initial contact of the molds with high pressure application after closing of the two molds.